Apparatus for grinding gears



Aug. 18, 1925.

w. a. FLANDERS APPARATLIS FOR GRINDING GEARS Filed April 10, 1920 INV NTOR.

\MBflangers BY ATTORNEY Patented Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

WARREN B. FLANDERS, OF ESSINGTON, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE GEAI t AND DYNAMOMETER COMPANY, A CORPORATION OF PENNSYLVANIA.

APPARATUS FOR GRINDING GEARS.

Application filed April 10, 1920. Serial No. 372,975. i

To all whom it may concern:

Be it known that I, WARREN B. FLANDERS, a citizen of the United States, and a resident of Essington, in the county of Delaware and State of Pennsylvania, have invented a new and useful Improvement in Apparatus for Grinding Gears, of which the following is a specification.

This invention relates to gear grinding apparatus, and particularly to apparatus employed in truing imperfectly cut teeth of reduction gearing, such as is commonly used for reducing the speed between a turbine and machinery adapted to operate at a greatly reduced speed. 1

It is practically impossible to cut the teeth of large reduction gears perfectly even though the greatest precaution is talzen in the construction of the gear cutting machinery and in the cutting operation. It is readily apparent that in a gear having say four hundred teeth, an error of a ten thousandths of an inch in the correct spacing of one tooth from another would make a cumulative error of forty one thousandths of an inch in the spacing of the last tooth cut with respect to the first one. It is the lili general practice to discard gears if the cumulative error is greater than six or eight one-thousandths of an inch, for the reason that heretofore it has been found impracticable to correct errors of greater magnitude to the degree of accuracy necessary in. gears of this type. Discarding a gear after it has been cut results in a considerable loss of time and labor, and it can readily be seen that such losses can easily occur when it is considered that-the maximum permissible error is only one fifty thousandth of an inch in the spacing of one tooth from another.

Gears having an error within the permissible limits have heretofore been partly corrected by' running under load the gear and pinion with which it is to operate while a mixture of oil and fine emery is constantly flowed over the gears at the point of contact. This operation tends-to grind every tooth practically the same amount, and, while local imperfections on each tooth are thereby corrected so that the tooth pressure is more evenly distributed throughout the length of the tooth, the error of the spacing is not materially corrected. It will be seen that if: a true pinion were driven at a constant speed and that the error in the spacing of the teeth of the gear meshed with the pinlon were one'iifty thousandth of an inch greater than it should be, the gear in making one revolution from the point of the first tooth cut to the last, or one complete revolution, would be turned eight thousandths of an inch further than the pinion would normally rotate the gear in the same number of revolutions of the pinion. Consequently the gear is either accelerated eight thousandths of an inch each revolution or the pinion is retarded correspondingly, resulting in. an uneven power delivery fluctuating between the point of least and greatest impact, or pressure, each revolution'of the gear. This action imposes excessive strains on certain teeth of the gear, while others are not functioning to their full capacity, with the result that the overloaded teeth become unduly worn and misshapen and injurious shocks are imparted to the driving and driven a aratus. Such misshapen teeth are also ha Is to fail internally and thus destroy the entire reduction gearing.

It is, therefore, the .object of my invention to provide improved apparatus for reducing or correcting errors in gearing in order to secure more satisfactory operation thereof.

These and other objects which will be made apparent throughout the further description are attained by means of gear grinding apparatus embodying. the features herein described and illustrated in the drawings accompanying and forming a part hereof; Wherein The single figure is a diagrammatic plan view of apparatus embodying the features of my invention.

Preferably and specifically stated, the ap-- i paratus comprises supporting members for the gear and also for the pinion with which the gear is to permanently operate. Suitable fly Wheels for driving the pinion in mesh with the gear at a constant speed by means of any preferred power agent are provided. The fly wheel secured to the gear is of such weight and diameter, that the ratio of bearing resistance to momentum is such that the relative angular velocity of the large gear with respect to that of the pinion is maintained substantially constant by means of the power translated by a single impulse of the pinion acting upon one or two teeth of the gear. In other words, the frictional losses of the bearing are not sufficient to reduce the speed of the gear sufficiently to bring the next highest tooth in contact with the pinion, and consequently only the high teeth will be engaged by the pinion, and the gear. will be driven through contact of the pinion with the high teeth only. As the teeth in contact become worn or reduced to the level of others, additional teeth will contact with the pinion, and so on until all of the teeth have been reduced to a shape and spacing such that all teeth of the gear are uniformly engaged by the pinion. A suitable abrasive, for example, a mixture of oil and fine emery, may be flowed over the gear at the point of contact for the purpose of facilitating the grinding action.

Referring to the drawing the apparatus for grinding the gears inclu es a rigid bearing frame 5 provided with three groups of rigidly mounted bearings 6 and 7, the former oup being adapted to support a pinion 8 etween a pair .of fly wheels 9 and 10 which are provided with shafts 11 and 12 respectively. The said shafts are supported by the bearings 7, and as shown, areprovided with couplings 13 for connecting the shafts to the shaft 14: and the pinion. The pinion 15' is secured to the shaft 11, and is driven by means of a gear 16 which may be operated by any suitable power agent capable of driving the shaft -11 at a substantially uniform velocity; The shaft 11 may, if desired, be directly connected to a suitable steam turbine or an electric motor.

'The apparatus also includes a fly wheel 23 having the shaft 17 supported in bearings 18. The shaft 17 is provided with a couplin 19 for the purpose of connecting the sai shaft directly to the shaft 20' of the gear 21, which, as shown, is the gear to be corrected. The gear is meshed with the pinion 8 and is supported in alignment with the shaft 17 by means of suitable bearings 22 disposed on either side of the gear.

When it is desired to grind a set, of reductiongearing the pinion is mounted in the bearings 6, and the shaft is connected to the flywheels on shafts 11 and 12 by means of (couplings 13. The gear is mounted in the bearings 22, and the shaft thereof is connected to the shaft 17 of the fly wheel 23 by means of the coupling 19. ,The shaft 11 is then rotated by any preferred power agent, and after .it has been accelerated to practicable working speed, the velocity of rotation is maintained constant. The gear to be corrected is concurrently accelerated by the pinion to the constant working speed, and as the bearinglfriction of the gear in opposition to the momentum thereof is relatively low, an engagement of the pinion with but a few hlghteeth of the. gear is all the power required to maintain a substantially uniform velocity rotation of the gear. As the gear and pinion are rotating at substantially relative velocities, the low teeth on the gear will not be engaged by the pinion until after the high teeth have been ground or reduced to the level and .shape of the lower teeth. The fly wheels 9 and 10 serve to steady speed of rotation of the pinionso that its velocity will not be materially reduced when the pinion is in working engage-' ment with the high teeth of the gear, or be materially accelerated when the inion is out of engagement with the gear. e gearing is thus driven until the high teeth have been reduced to the level of the lowest 01 until the teeth are all of uniform shape and spacing.

The expression high teeth, as used herein and as well understood in the art, is intended to designate those teeth which are thicker or are slightly larger circumferentially than others and is not used either ing contrivance; and, in the drawings, the

momentum members comp-rise the fly-wheels 9, 10, and 23 carried by the shafts 11, 12, and 17 respectively, although it is to be understood that any suitable construction giving a fly-wheel effect may be used in so far as my invention is concerned in its broadest aspect.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereo and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim'is 1. In apparatus for grinding meshing pinion and gear members, the combination of momentum members connected to opposite ends of the pinion member and to one end of the gear 'member and means for' driving one of the momentum members.

2. In apparatus for" grinding meshing pinion and gear members mounted on supporting shafts, the combination of a plurality of fly-wheels, shafts for the fly-wheels, couplings for connecting the latter shafts to the gear and pinion supportin shafts, bination of a. supporting frame, momentum 10 and means for driving one of the y-wheel members supported by the frame, and a plushafts. rality of gear member supporting bearings 3. In a gear grinding machine, the comarranged between the momentum members.

6 bination of a supporting frame, a momentum In testimony whereof, I have hereunto member carried by the frame and gear memsubscribed my name this 7th day of April, 15 her supporting bearings alined with the axis 1920. of the momentum member.

, 4. In a gear grinding machine, the oom- I WARREN B. FLANDERS. 

